Earthing... yes another thread

[Ihopethisworks]

Got a quick (i hope) few questions...

I am intending on replacing my current plastic bath with a steel enamel coated one. And I have some questions on earthing requirements.

My mains water, gas, hot, flow and return are all copper throughout and are bonded together. The gas is connected to an earth block near the meter which is in turn connected to the earth from the ground. All via earth cables... done when house was re-wired (by a qualified sparky).

I understand my bath needs earth connection, as I assume that all my pipes are already at earth which are in turn connected to the bath is not sufficient?

Can I simply connect the bath with the earth cable to the pipes (using the clips) or do I have to have go back to earth block? If I have to go back to the earth block, can some please explain why?

Is this work notifiable to my BC? I understand that I can legally do this myself?

I am also considering installing a bathroom radiator, does this need to be earthed even though the pipes to it are already 'at earth'?

 

[EFLImpudence]

Probably not but firstly, please tell us if ALL the electrical circuits in the bathroom are protected by a Residual Current Device?

 

[333rocky333]

Only extraneous conductive parts connect to the earth block, possibly a metal waste pipe,

Other pipework is classed as bonding and usually confined to the bathroom and not connected to the earth block

 

[Ihopethisworks]

Probably not but firstly, please tell us if ALL the electrical circuits in the bathroom are protected by a Residual Current Device?

Yes, all circuits in the whole house are.

 

[Taylortwocities]

Probably not but firstly, please tell us if ALL the electrical circuits in the bathroom are protected by a Residual Current Device?

Yes, all circuits in the whole house are.

In that case, no bonding is necessary in the bathroom and that includes your new bath.

 

[Ihopethisworks]

Probably not but firstly, please tell us if ALL the electrical circuits in the bathroom are protected by a Residual Current Device?

Yes, all circuits in the whole house are.

In that case, no bonding is necessary in the bathroom and that includes your new bath.

Thanks... for my personal benefit, I assume that means that the pipes to the bath act as the earth for the bath? Or is it no longer deemed a safety risk to have a metal bath not earthed? Just want to understand why, if possible.

 

[Taylortwocities]

The process is not earthing
it is called supplementary equipotential bonding

There's a whole treatise on this on the WIKI
see //www.diynot.com/wiki/electric...l_bonding:supplementary_equipotential_bonding

But since ye 17th edition of the regs in general you don't need it if all circuits in your bathroom are RCD protected and your main services are bonded.
See //www.diynot.com/wiki/electrics:speclcn:supbond17th




blithely

 

[bernardgreen]

Given the the small cost of bonding the metal bath to the pipes supplying the taps I would fit that bond. It would give me peace of mind that in a fault situation the bath was still a safe place.

Taps do not always make a good electrical connection to an enamalled bath due to the enamel on top and the rubber sealing ring underneath being insulators.

The area, walls and floor around a bath is often damp and this could provide a route for voltage from a damaged cable or fitting to reach the bath putting the bath at a different voltage to its taps. If this happens them someone in the bath will get a mild to severe tingle when they touch the taps.

That tingle is un-likely to be fatal though it might cause a fall that leads to serious injury. The current causing the tingle, earth leakage through the body, is un-likely to be sufficient to trip the RCD. Even though the enamel insulates the water from direct contact with the metal of the bath the capacitive coupling between bath and water is high.

 

[Ihopethisworks]

Given the the small cost of bonding the metal bath to the pipes supplying the taps I would fit that bond. It would give me peace of mind that in a fault situation the bath was still a safe place.

Thanks, I will do that, better safe than sorry. In my view the enamel could get chipped and create a direct path between water and metal.

 

[Electrifying]

Given the the small cost of bonding the metal bath to the pipes supplying the taps I would fit that bond. It would give me peace of mind that in a fault situation the bath was still a safe place.

Taps do not always make a good electrical connection to an enamalled bath due to the enamel on top and the rubber sealing ring underneath being insulators.

The area, walls and floor around a bath is often damp and this could provide a route for voltage from a damaged cable or fitting to reach the bath putting the bath at a different voltage to its taps. If this happens them someone in the bath will get a mild to severe tingle when they touch the taps.

That tingle is un-likely to be fatal though it might cause a fall that leads to serious injury. The current causing the tingle, earth leakage through the body, is un-likely to be sufficient to trip the RCD. Even though the enamel insulates the water from direct contact with the metal of the bath the capacitive coupling between bath and water is high.

Yes, and given the small cost of that bond, you might as well bond your metal loo roll holder - along with your metal toothbrush holder...........oh, and don't forget your door handle.

Why don't we give advice according to the regulations - instead of making it up as we go along........that way, everyone should apply the same practices.



Is the bath an 'extraneous conductive part' - i.e. does it introduce a potential to the bathroom??

NO - so it doesn't require bonding.

Is the bath an 'exposed conductive part' - i.e. is it part of an electrical installation that could become live under fault conditions??

NO - so it doesn't require earthing.

Randomly earthing/bonding metal objects can sometimes create hazards that weren't there in the first place.

 

[bernardgreen]

Why don't we give advice according to the regulations - instead of making it up as we go along........that way, everyone should apply the same practices.

Why do the regulations change from edition to edition ?

Could the answer to that be that the regulations are a compromise between what is essential for safety and cost and work involved. Why was there a time when metal baths had ( or were strongly recommended ) to be bonded ?

Could the answer be that before RCDs were cheap and easily available bonding the bath was safer than no bond. ?

Just adding a safety device should not remove other common sense safety actions from the regulations but it seems it does.

Is the bath an 'extraneous conductive part' - i.e. does it introduce a potential to the bathroom??

No it is not under NORMAL conditions.

NO - so it doesn't require bonding.

...Under normal conditions but may if conditions become ab-normal.

Is the bath an 'exposed conductive part' - i.e. is it part of an electrical installation that could become live under fault conditions??

Yes it could become connected to a hazardous voltage under fault conditions.

NO - so it doesn't require earthing.

No is an incorrect answer for some fault conditions.

Randomly earthing/bonding metal objects can sometimes create hazards that weren't there in the first place.

True but not when "random" is replaced by common sense, basic electrical theory and knowledge of what faults can occur. As we know bonding the pipe work of an outside tap to the MET of a PMR system can create a hazard for anyone touching the tap ( or gas meter ) when standing on the ground outside the equi-potential zone created by the bonding regulations. Also why all electrical equipment used in the garden must be double insulated and NOT have metal that can possibly be earthed via the cable in case it is used on a PME system where the network neutral goes open or faulty.

 

[mikhailfaradayski]

Hi, Just wondering something.

I have some spoons in my kitchen, in the event that the wall near my sink becomes damp and there is a faulty cable which could possibly make the wall slightly live then i make a cup of tea in an old enamel cup but the cup accidentally touches the wall which is damp and live at the same time as I'm stirring my cuppa, will i get a shock?

Do I need to bond my spoons?

 

[ban-all-sheds]

Why was there a time when metal baths had ( or were strongly recommended ) to be bonded ?

Like this sort?

 

[EFLImpudence]

Given the the small cost of bonding the metal bath to the pipes supplying the taps I would fit that bond. It would give me peace of mind that in a fault situation the bath was still a safe place.

You have written 'bonding'...

Taps do not always make a good electrical connection to an enamalled bath due to the enamel on top and the rubber sealing ring underneath being insulators.

...but it would seem you are meaning 'earthing' - that which would cause the OPD to operate should the bath become live.

This is not the purpose of 'bonding'. We do not 'bond' in case the bath becomes live.
Edit. I should rephrase that. We do not 'bond' in case the bath should be touched by a live conductor.

However, it is 'bonding' about which we are being asked.

Should the taps make a zero resistance join then there is no need for extra 'bonding' to equalise potential.
Should the join (between taps and bath) be of some resistance then this would be advantageous.

Totally insulated (infinite resistance) would be the ideal as there would be no path to earth should a person touch a faulty live part with one hand and the bath with the other.

 

[bernardgreen]

So it would seem that the same piece of wire can be either a bond or an "earth" depending on which fault occurs to affect the bath.

If there is a LOW impedance fault connection between a live conductor and the bath then the wire is an EARTH that carries enough current to trip an over current device.

If there is a HIGH impedance fault connection between a live conductor and the bath then the wire is an BOND that carries enough current to keep the bath at the same potential as other metal work in the bathroom. This current may not be enough to trip an RCD